Written by: Emily J., MSc RD
Reviewed by: Dr. Vimal Ramjee, MD, FACC
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Sleep is foundational to your metabolic health — a lack of sleep or irregular sleep can have a significant impact on glucose levels, insulin sensitivity, weight, and hormones.
We know that sleep is crucial for physical and mental recovery, but it also has a significant relationship with your metabolic health and can help or harm markers of metabolic health such as fasting glucose, insulin resistance, and weight. It also regulates hormones that signal hunger and satiety and supports efficient glucose metabolism.
When we’re feeling overwhelmed, stressed, burnt out at work, sick, or just plain exhausted, the advice we’re often given is, “You should get some sleep.”
However, this may be easier said than done. The CDC reports that more than 1 in 3 Americans are sleep deprived , and it’s estimated that sleep-related issues, like trouble falling asleep, staying asleep, and sleep disorders, affect around 50-70 million Americans [1, 2].
This is problematic because sleep is strongly tied to metabolic health, and over time, poor sleep may contribute to the deterioration of metabolic health.
So how do we fix this?
The general recommendation for the amount of sleep you need each night is 7-9 hours, though this may vary between individuals and depends on if you’ve skimped on sleep lately.
The normal sleep state reduces your metabolic rate, or the number of calories you’re burning, by around 15-35%, with your metabolic rate being the lowest during deep sleep . This allows the body to recover and repair cells from the “work” of the day.
Glucose utilization decreases during deep sleep due to the reduced activity of neurons . Between 4-8am, glucose is released from the liver in preparation for your body being active, so glucose levels tend to be higher in the morning .
However, when sleep becomes abnormal, whether because of sleep deprivation or an irregular sleep schedule, problems begin to arise.
Sleep deprivation is a term for any instance where you don’t sleep for long enough or don’t get enough high-quality sleep due to restlessness, waking up frequently, or not enough deep sleep.
In studies where subjects experienced total sleep deprivation (i.e., they were kept awake for anywhere from 24-120 consecutive hours), they experienced increased fasting glucose, reduced glucose tolerance, and decreased energy metabolism . In the longest sleep deprivation condition, subjects even began to show muscle metabolism that was similar to someone with prediabetes.
In other total sleep deprivation studies, participants saw increased fasting insulin levels and poor insulin response to glucose, indicating insulin resistance .
But it’s not just these sleep extremes that affect metabolic health.
In partial sleep deprivation studies, where subjects slept anywhere from 4-6 hours a night, researchers found that participants experienced decreased glucose tolerance, a 30% decrease in insulin response to glucose, and increased insulin resistance .
Another study looking at just 2 nights of partial sleep deprivation showed a reduction in glucose tolerance and reduced insulin action , suggesting that just a few nights of missed sleep can start to affect your metabolic health, and a week of sleep deprivation can begin to have significant impacts on metabolic health.
The evidence is clear: sleep deprivation is linked to key markers of metabolic health. One night of poor sleep may be something you see reflected in your glucose levels the next day.
Beyond losing sleep, what about your sleep schedule? Does it matter what time you go to sleep and wake up each day?
New research suggests that it does.
Not having a regular sleep schedule and varying the time you sleep each night increases the risk of obesity, high blood pressure, and high blood glucose levels. Every hour of bedtime/rise time variability resulted in a ~30% increase in the potential for an abnormal metabolic health response .
Sleep directly impacts metabolic health, blood glucose, and insulin resistance, but the good news is that the damage done by lost sleep is not irreversible.
In shorter-term sleep debt, about 2 nights of adequate sleep can get you back to baseline. However, chronic sleep deprivation requires more research to understand how recovery works, and will likely take longer than a few nights of recovery sleep to normal metabolic rhythms during sleep.
In the meantime, try to pick a 30-minute (or smaller!) window for your bedtime and wake time that you can stick to in order to maintain or improve your sleep and metabolic health.
Sleep is a major player when it comes to maintaining stable blood glucose, increasing insulin resistance, and improving metabolic health. Of course, other lifestyle habits, like the food we eat and our exercise pattern, are linked with how well (or poorly) we sleep. So how can you improve your sleep to better serve your metabolic health?
When you implement new sleep habits, you may find energy levels rising and mental acuity improving. Monitoring your blood glucose with a CGM can also be helpful to see how your sleep patterns affect blood glucose levels and how blood glucose is improved by getting better sleep.